This invention relates generally to the field of transmembrane delivery of drugs or bioactive molecules to an organism. More particularly, this invention relates to a minimally invasive to non-invasive method of increasing the permeability of the skin, mucosal membrane or outer layer of a plant through microporation of this biological membrane, which can be combined with sonic, electromagnetic, and thermal energy, chemical permeation enhancers, pressure, and the like for selectively enhancing flux rate of bioactive molecules into the organism and, once in the organism, into selected regions of the tissues therein.
The stratum corneum is chiefly responsible for the well known barrier properties of skin. Thus, it is this layer that presents the greatest barrier to transdermal flux of drugs or other molecules into the body and of analytes out of the body. The stratum corneum, the outer horny layer of the skin, is a complex structure of compact keratinized cell remnants separated by lipid domains. Compared to the oral or gastric mucosa, the stratum corneum is much less permeable to molecules either external or internal to the body. The stratum corneum is formed from keratinocytes, which comprise the majority of epidermal cells, that lose their nuclei and become comeocytes. These dead cells comprise the stratum corneum, which has a thickness of only about 10-30 xcexcm and, as noted above, is a very resistant waterproof membrane that protects the body from invasion by exterior substances and the outward migration of fluids and dissolved molecules. The stratum corneum is continuously renewed by shedding of corneum cells during desquamination and the formation of new corneum cells by the keratinization process.
Underlying the stratum corneum is the viable cell layer of the epidermis and the dermis, or connective tissue layer. These layers together make up the skin. Microporation of these underlying layers (the viable cell layer and dermis) has not previously been used but may enhance transdermal flux. Deep to the dermis are the underlying structures of the body, including fat, muscle, bone, etc.
Microporation of the mucous membrane has not been used previously. The mucous membrane generally lacks a stratum corneum. The most superficial layer is the epithelial layer which consists of numerous layers of viable cells. Deep to the epithelial layer is the lamina propria, or connective tissue layer.
Microporation of plants has been previously limited to select applications in individual cells in laboratory settings. Plant organisms generally have tough outer layers to provide resistance to the elements and disease. Microporation of this tough outer layer of plants enables the delivery of substances useful for introduction into the plant such as for conferring the desired trait to the plant or for production of a desired substance. For example, a plant may be treated such that each cell of the plant expresses a particular and useful peptide such as a hormone or human insulin.
The flux of a drug or analyte across the biological membrane can be increased by changing either the resistance (the diffusion coefficient) or the driving force (the gradient for diffusion). Flux may be enhanced by the use of so-called penetration or chemical enhancers. Chemical enhancers are well known in the art and a more detailed description will follow.
Another method of increasing the permeability of skin to drugs is iontophoresis. Iontophoresis involves the application of an external electric field and topical delivery of an ionized form of drug or an un-ionized drug carried with the water flux associated with ion transport (electro-osmosis). While permeation enhancement with iontophoresis has been effective, control of drug delivery and irreversible skin damage are problems associated with the technique.
Sonic energy has also been used to enhance permeability of the skin and synthetic membranes to drugs and other molecules. Ultrasound has been defined as mechanical pressure waves with frequencies above 20 kHz, H. Lutz et al., Manual of Ultrasound 3-12 (1984). Sonic energy is generated by vibrating a piezoelectric crystal or other electromechanical element by passing an alternating current through the material, R. Brucks et al., 6 Pharm. Res. 697 (1989). The use of sonic energy to increase the permeability of the skin to drug molecules has been termed sonophoresis or phonophoresis.
Although it has been acknowledged that enhancing permeability of the skin should theoretically make it possible to transport molecules from inside the body through the skin to outside the body for collection or monitoring, practicable methods have not been disclosed. U.S. Pat. No. 5,139,023 to Stanley et al. discloses an apparatus and method for noninvasive blood glucose monitoring. In this invention, chemical permeation enhancers are used to increase the permeability of mucosal tissue or skin to glucose. Glucose then passively diffuses through the mucosal tissue or skin and is captured in a receiving medium. The amount of glucose in the receiving medium is measured and correlated to determine the blood glucose level. However, as taught in Stanley et al., this method is much more efficient when used on mucosal tissue, such as buccal tissue, which results in detectable amounts of glucose being collected in the receiving medium after a lag time of about 10-20 minutes. However, the method taught by Stanley et al. results in an extremely long lag time, ranging from 2 to 24 hours depending on the chemical enhancer composition used, before detectable amounts of glucose can be detected diffusing through human skin (heat-separated epidermis) in vitro. These long lag times may be attributed to the length of time required for the chemical permeation enhancers to passively diffuse through the skin and to enhance the permeability of the barrier stratum corneum, as well as the length of time required for the glucose to passively diffuse out through the skin. Thus, Stanley et al. clearly does not teach a method for tnsporting blood glucose or other analytes non-invasively through the skin in a manner that allows for rapid monitoring, as is required for blood glucose monitoring of diabetic patients and for many other body analytes such as blood electrolytes.
While the use of sonic energy for drug delivery is known, results have been largely disappointing in that enhancement of permeability has been relatively low. There is no consensus on the efficacy of sonic energy for increasing drug flux across the skin. While some studies report the success of sonophoresis, J. Davick et al., 68 Phys. Ther. 1672 (1988); J. Griffin et al., 47 Phys. Ther. 594 (1967); J. Griffin and J. Touchstone, 42 Am. J. Phys. Med. 77 (1963); J. Griffin et al., 44 Am. J. Phys. Med. 20 (1965); D. Levy et al., 83 J. Clin. Invest. 2074); D. Bommannan et al., 9 Pharm. Res. 559 (1992), others have obtained negative results, H. Benson et al., 69 Phys. Ther. 113 (1988); J. McElnay et al., 20 Br. J. Clin. Pharmacol. 4221 (1985); H. Pratzel et al., 13 J. Rheumatol. 1122 (1986). Systems in which rodent skin were employed showed the most promising results, whereas systems in which human skin was employed have generally shown disappointing results. It is well known to those skilled in the art that rodent skin is much more permeable than human skin, and consequently the above results do not teach one skilled in the art how to effectively utilize sonophoresis as applied to transdermal delivery and/or monitoring through human skin.
A significant improvement in the use of ultrasonic energy in the monitoring of analytes and also in the delivery of drugs to the body is disclosed and claimed in copending applications Ser. No. 08/152,442 filed Nov. 15, 1993, now U.S. Pat. No. 5,458,140, and Ser. No. 08/152,174 filed Dec. 8, 1993, now U.S. Pat. No. 5,445,61 1, both of which are incorporated herein by reference. In these inventions, the transdermal sampling of an analyte or the transdermal delivery of drugs, is accomplished through the use of sonic energy that is modulated in intensity, phase, or frequency or a combination of these parameters coupled with the use of chemical permeation enhancers. Also disclosed is the use of sonic energy, optionally with modulations of frequency, intensity, and/or phase, to controllably push and/or pump molecules through the stratum corneum via perforations introduced by needle puncture, hydraulic jet, laser, electroporation, or other methods.
The formation of micropores (i.e. microporation) in the stratum corneum to enhance the delivery of drugs has been the subject of various studies and has resulted in the issuance of patents for such techniques.
Jacques et al., 88 J. Invest. Dermatol. 88-93 (1987), teaches a method of administering a drug by ablating the stratum corneum of a region of the skin using pulsed laser light of wavelength, pulse length, pulse energy, pulse number, and pulse repetition rate sufficient to ablate the stratum corneum without significantly damaging the underlying epidermis and then applying the drug to the region of ablation. This work resulted in the issuance of U.S. Pat. No. 4,775,361 to Jacques et al. The ablation of skin through the use of ultraviolet-laser irradiation was earlier reported by Lane et al., 121 Arch. Dermatol. 609-617 (1985). Jacques et al. is restricted to use of few wavelengths of light and expensive lasers.
Tankovich, U.S. Pat. No. 5,165,418 (hereinafter, xe2x80x9cTankovich ""418xe2x80x9d), discloses a method of obtaining a blood sample by irradiating human or animal skin with one or more laser pulses of sufficient energy to cause the vaporization of skin tissue so as to produce a hole in the skin extending through the epidermis and to sever at least one blood vessel, causing a quantity of blood to be expelled through the hole such that it can be collected. Tankovich ""418 thus is inadequate for noninvasive or minimally invasive permeabilization of the stratum corneum such that a drug can be delivered to the body or an analyte from the body can be analyzed.
Tankovich et al., U.S. Pat. No. 5,423,803 (hereinafter, xe2x80x9cTankovich ""803xe2x80x9d) discloses a method of laser removal of superficial epidermal skin cells in human skin for cosmetic applications. The method comprises applying a light-absorbing xe2x80x9ccontaminantxe2x80x9d to the outer layers of the epidermis and forcing some of this contaminant into or through the intercellular spaces in the stratum corneum, and illuminating the infiltrated skin with pulses of laser light of sufficient intensity that the amount of energy absorbed by the contaminant will cause the contaminant to explode with sufficient energy to tear off some of the epidermal skin cells. Tankovich ""803 further teaches that there should be high absorption of energy by the contaminant at the wavelength of the laser beam, that the laser beam must be a pulsed beam of less than 1 xcexcs duration, that the contaninant must be forced into or through the upper layers of the epidermis, and that the contaminant must explode with sufficient energy to tear off epidermal cells upon absorption of the laser energy. This invention also fails to disclose or suggest a method of drug delivery or analyte collection.
Raven et al., WO 92/00106, describes a method of selectively removing unhealthy tissue from a body by administering to a selected tissue a compound that is highly absorbent of infiared radiation of wavelength 750-860 nm and irradiating the region with corresponding infrared radiation at a power sufficient to cause thermal vaporization of the tissue to which the compound was administered but insufficient to cause vaporization of tissue to which the compound had not been administered. The absorbent compound should be soluble in water or serum, such as indocyanine green, chlorophyll, porphyrins, heme-containing compounds, or compounds containing a polyene structure, and power levels are in the range of 50-1000 W/cm2 or even higher.
Konig et al., DD 259351, teaches a process for thermal treatment of tumor tissue that comprises depositing a medium in the tumor tissue that absorbs radiation in the red and/or near red infrared spectral region, and irradiating the infiltrated tissue with an appropriate wavelength of laser light. Absorbing media can include methylene blue, reduced porphyrin or its aggregates, and phthalocyanine blue. Methylene blue, which strongly absorbs at 600-700 nm, and a krypton laser emitting at 647 and 676 nm are exemplified. The power level should be at least 200 mW/cm2.
It has been shown that by stripping the stratum corneum from a small area of the skin with repeated application and removal of cellophane tape to the same location one can easily collect arbitrary quantities of interstitial fluid, which can then be assayed for a number of analytes of interest. Similarly, the xe2x80x98tape-strippedxe2x80x99 skin has also been shown to be permeable to the ansdermal delivery of compounds into the body. Unfortunately, xe2x80x98tape-strippingxe2x80x99 leaves a open sore which takes weeks to heal, and for this, as well as other reasons, is not considered as an acceptable practice for enhancing transcutaneous transport in wide applications.
As discussed above, it has been shown that pulsed lasers, such as the excimer laser operating at 193 nm, the erbium laser operating near 2.9 xcexcm or the CO2 laser operating at 10.2 xcexcm, can be used to effectively ablate small holes in the human stratum corneum. These laser ablation techniques offer the potential for a selective and potentially non-traumatic method for opening a delivery and/or sampling hole through the stratum corneum. However, due to the prohibitively high costs associated with these light sources, there have been no commercial products developed based on this concept. The presently disclosed invention, by defining a method for directly conducting thermal energy into or through the biological membrane with very tightly defined spatial and temporal resolution, makes it possible to produce the desired micro-ablation of the biological membrane very low cost energy sources.
In view of the foregoing problems and/or deficiencies, the development of a method for safely enhancing the permeability of the biological membrane for minimally invasive or noinvasive monitoring of body analytes in a more rapid time frame would be a significant advancement in the art. It would be another significant advancement in the art to provide a method of minimally invasively or non-invasively enhancing the transmembrane flux rate of a drug into a selected area of an organism.
Significant advancements in the delivery of drugs and other compounds are being made through the use of various techniques that increase the permeability of a biological membrane, such as the skin or mucosal membrane. Even more promising advances have been made through techniques for creating micropores, as disclosed in the aforementioned applications.
Nevertheless, it is desirable to improve upon these technologies by forming micropores at selected depths in the biological membrane and to deliver both small and large compounds, in terms of molecular weight and size, through the micropores into the body.
This invention provides a method for enhancing the transmembrane flux rate of a permeant into a selected site of an organism comprising the steps of enhancing the permeability of said selected site of the organism to said permeant by means of (a) porating a biological membrane at said selected site by means that form a micropore in said biological membrane, thereby reducing the barrier properties of said biological membrane to the flux of said permeant and (b) contacting the porated selected site with a composition comprising an effective amount of said permeant, whereby the transmembrane flux rate of said permeant into the organism is enhanced.
This invention futher provides the method of enhancing the transmembrane flux rate further comprising applying to said site of said organism an enhancer to increase the flux of said permeant into said organism. The invention also provides the method wherein said enhancer comprises sonic energy, and more specifically, wherein the said sonic energy is applied to said site at a frequency in the range of about 10 Hz to 1000 MHz, and wherein said sonic energy is modulated by means of a member selected from the group consisting of frequency modulation, amplitude modulation, phase modulation, and combinations thereof. Alternatively, the said enhancer comprises an electromagnetic field, and, more specifically, iontophoresis or a magnetic field., or a mechanical force, chemical enhancer, or thermal enhancer. Additionally, the invention further provides a method wherein any of the methods of sonic, electromagnetic, mechanical, thermal, or chemical enhancement may be applied in any combination thereof to increase the transmembrane flux rate of said permeant into or through said micropore.
This invention also provides a method of further enhancing the transmembrane flux rate with an enhancer, wherein said enhancers at said site are applied so as to increase the flux rate of the permeant into tissues surrounding the micropore. The said enhancer can comprise sonic energy. Furthermore, the said sonic energy is applied to said site at a frequency in the range of about 10 Hz to 1000 MHz, wherein said sonic energy is modulated by mens of a member selected from the group consisting of frequency modulation, amplitude modulation, phase modulation, and combinations thereof. Alternatively, the said enhancer comprises sonic or thermal energy, electroporation, iontophoresis, chemical enhancers, mechanical force, or a magnetic field, or any combination thereof.
The invention further includes the method of enhancing the transmembrane flux rate of a permeant further comprising applying to said site of said organism an enhancer, wherein any of the methods of methods of sonic or thermal energy, electroporation, iontophoresis, chemical enhancers, mechanical force, or a magnetic field may be applied in any combination thereof further comprising the method of combining sonic or thermal energy, electroporation, iontophoresis, chemical enhancers, mechanical force, or a magnetic field to increase the flux rate of the permeant into tissues surrounding the micropore.
The invention also includes the method of further enhancing the tranmembrane flux rate within and beneath the outer layer wherein said porating of said biological membrane in said site is accomplished by means selected from the group consisting of (a) ablating the biological membrane by contacting said site, up to about 1000 xcexcm across, of said biological membrane with a heat source such that a micropore is formed in said biological membrane at said site; (b) puncturing said biological membrane with a micro-lancet calibrated to form a micropore of up to about 1000 xcexcm in diameter; (c) ablating the biological membrane by a beam of sonic energy onto said biological membrane up to about 1000 xcexcm in diameter; (d) hydraulically puncturing said biological membrane with a high pressure jet of fluid to form a micropore of up to about 1000 xcexcm in diameter and (e) puncturing said biological membrane with short pulses of electricity to form a micropore of up to about 1000 xcexcm in diameter. Further, the invention includes the method wherein said porating is accomplished by contacting said site, up to about 1000 xcexcm across, with a heat source to conductively transfer an effective amount of thermal energy to said site such that the temperature of some of the water and other vaporizable substances in said site is elevated above their vaporization point creating a micropore to a selected depth in the biological membrane at said site or wherein said porating is accomplished by contacting said site, up to about 1000 xcexcm across, with a heat source to conductively tansfer an effective amount of thermal energy to said site such that the temperature of some of the tissue at said site is elevated to the point where thermal decomposition occurs creating a micropore to a selected depth in the biological membrane at said site. Additionally, the invention includes the method of porating said biological membrane in said site further comprising treating at least said site with an effective amount of a substance that exhibits sufficient absorption over the emission range of a pulsed light source and focusing the output of a series of pulses from said pulsed light source onto said substance such that said substance is heated sufficiently to conductively transfer an effective amount of thermal energy to said biological membrane to elevate the temperature to thereby create a micropore. The invention also includes the method wherein said pulsed light source emits at a wavelength that is not significantly absorbed by said biological membrane. The invention further provides the method wherein said pulsed light source is a laser diode emitting in the range of about 630 to 1550 nm, wherein said pulsed light source is a laser diode pumped optical parametric oscillator emitting in the range of about 700 and 3000 nm, wherein said pulsed light source is a member selected from the group consisting of arc lamps, incandescent lamps, and light emitting diodes. The invention also includes the method further comprising providing a sensing system for determining when the micropore in the biological membrane has reached the desired dimensions, including width, length, and depth, and, further, wherein said sensing system comprises light collection means for receiving light reflected from said site and focusing said reflected light on a detector for receiving said light and sending a signal to a controller wherein said signal indicates a quality of said light, and a controller coupled to said detector and to said light source for receiving said signal and for shutting off said light source when a preselected signal is received, or, alternatively, an electrical impedance measuring system which can detect the changes in the impedance of the biological membrane at different depths into the organism as the micropore is formed.
The invention also provides the method of enhancing the tranmembrane flux rate within and beneath the outer layer further comprising cooling said site and adjacent tissues such that said site and adjacent tissues are in a cooled condition. The said cooling means comprises a Peltier device.
The invention also includes the method of enhancing the transmembrane flux within and beneath the outer layer further comprising, prior to porating said site, illuminating at least said site with light such that said site is sterilized.
This invention also includes the method of enhancing the transmembrane flux within and beneath the outer layer further comprising contac ting said site with a solid element, wherein said solid element functions as a heat source to conductively transfer an effective amount of thermal energy to said biological membrane to elevate the temperature to thereby create a micropore. Further, said heat source is constructed to modulate the temperature of said site to greater than 100xc2x0 C. within about 10 nanoseconds to 50 millisecond s and then returning the temperature of said site to approximately ambient temperature within about 1 millisecond to 50 milliseconds and wherein a cycle of raising the temperature and returning to ambient temperature is repeated one or more times effective for porating the biological membrane to the desired depth. The invention further includes the method of using a heat source wherein said returning to approximately ambient temperature of said site is carried out by withdrawing said heat source from contact with said site and wherein the modulation parameters are selected to reduce sensation to the animal subject.
The invention includes the method for enhancing transmembrane flux rates using a heat source and sensing system further comprising providing means for monitoring electrical impedance between said solid element and said organism through said site and adjacent tissues and means for advancing the position of said solid element such that as said poration occurs with a concomitant change in impedance, said advancing means advances the solid element such that the solid element is in contact with said site during heating of the solid element, until the selected impedance is obtained. Further, the invention includes this method further comprising means for withdrawing said solid element from contact with said site wherein said monitoring means is capable of detecting a change in impedance associated with contacting a selected layer underlying the surface of said site and sending a signal to said withdrawing means to withdrawn said solid element from contact with said site.
The method of enhancing the transmembrane flux rate using a solid element wherein said solid element is heated by delivering an electrical current through an ohmic heating element and, further, wherein said solid element is formed such that it contains an electrically conductive component and the temperature of said solid element is modulated by passing a modulated electrical current through said conductive element. Additionally, the invention includes the method wherein said solid element is positioned in a modulatable magnetic field wherein energizing the magnetic field produces electrical eddy currents sufficient to heat the solid element.
The invention also includes the method of enhancing the transmembrane flux rate wherein said porating is accomplished by puncturing said site with a micro-lancet calibrated to form a micropore of up to about 1000 xcexcm in diameter, by a beam of sonic energy directed onto said site to form a micropore of up to about 1000 xcexcm in diameter, by hydraulically puncturing said biological membrane with a high pressure jet of fluid to form a micropore of up to about 1000 xcexcm in diameter, or, alternatively, by puncturing said biological membrane with short pulses of electricity to form a micropore of up to about 1000 xcexcm in diameter.
The invention further comprises the method of enhancing the transmembrane flux rate of a permeant wherein said permeant comprises a nucleic acid. More specifically, the invention includes the method wherein said nucleic acid comprises DNA or wherein the nucleic acid comprises RNA.
The invention further includes the method of enhancing the transmembrane flux rate of a permeant wherein the micropore in the biological membrane extends into a portion of the outer layer of the biological membrane ranging from 1 to 30 microns in depth, extends through the outer layer of the biological membrane ranging from 10 to 200 microns in depth, extends into the connective tissue layer of the biological membrane ranging from 100 to 5000 microns in depth, or extends through the connective tissue layer of the biological membrane ranging from 1000 to 10000 microns in depth.
The invention further includes the method of enhancing the transmembrane flux rate of a permeant, wherein the micropore penetrates the biological membrane to a depth determined to facilitate desired activity of the selected permeant.
The invention further includes the method of enhancing the transmembrane flux rate of a permeant wherein the permeant comprises a polypeptide, including wherein the polypeptide is a protein or a peptide, and further including wherein the peptide comprises insulin or a releasing factor; a carbohydrate, including wherein the carbohydrate comprises a heparin; an analgesic, including wherein the analgesic comprises an opiate; a vaccine; or a steroid.
The invention further includes the method of enhancing the transmembrane flux rate of a permeant wherein the permeant is associated with a carrier. The invention further includes the method wherein the carrier comprises liposomes; lipid complexes; microparticles; or polyethylene glycol compounds. More specifically, the invention further includes the method wherein the permeant is a vaccine in combination with the method wherein the permeant is associated with a carrier.
The invention further includes the method of enhancing the transmembrane flux rate of a permeant wherein the permeant comprises a substance which has the ability to change its detectable response to a stimulus when in the proximity of an analyte present in the organism.
An object of the invention is to provide a method for controlling transmembrane flux rates of drugs or other molecules into the body and, if desired, into the bloodstream through minute perforations in the biological membrane, including stratum corneum or other layers of the skin or in the mucosa or outer layers of a plant.
It is still another object of the invention to provide a method of delivering drugs into the body through micropores in the biological membrane in combination with sonic energy, permeation enhancers, pressure gradients, electromagnetic energy, thermal energy, and the like.
An object of the invention is to minimize the barrier properties of the biological membrane using poration to controllably collect analytes from within the body through perforations in the biological membrane to enable the monitoring of these analytes.
It is also an object of the invention to provide a method of monitoring selected analytes in the body through micropores in the biological membrane in combination with sonic energy, permeation enhancers, pressure gradients, electromagnetic energy, mechanical energy, thermal energy, and the like.
These and other objects may be accomplished by providing a method for monitoring the concentration of an analyte in an individual""s body comprising the steps of enhancing the permeability of the biological membrane of a selected area of the individual""s body surface to the analyte by means of
(a) porating the biological membrane of the selected area by means that form a micropore in the biological membrane optionally without causing serious damage to the underlying tissues, thereby reducing the barrier properties of the biological membrane to the withdrawal of the analyte;
(b) collecting a selected amount of the analyte; and
(c) quantitating the analyte collected.
In one preferred embodiment, the method further comprises applying sonic energy to the porated selected area at a frequency in the range of about 5 kHz to 100 MHz, wherein the sonic energy is modulated by means of a member selected from the group consisting of frequency modulation, amplitude modulation, phase modulation, and combinations thereof In another preferred embodiment, the method comprises contacting the selected area of the individual""s body with a chemical enhancer with the application of electromagnetic, thermal, mechanical, or sonic energy to further enhance analyte withdrawal.
Porating of the biological membrane is accomplished by means selected from the group consisting of (a) ablating the biological membrane by contacting a selected area, up to about 1000 xcexcm across, of the biological membrane with a heat source such that the temperature of tissue-bound water and other vaporizable substances in the selected area is elevated above the vaporization point of the water and other vaporizable substances thereby removing the biological membrane in the selected area; (b) puncturing the biological membrane with a micro-lancet calibrated to fonn a micropore of up to about 1000 xcexcm in diameter; (c) ablating the biological membrane by focusing a tightly focused beam of sonic energy onto the stratum corneum; (d) hydraulically puncturing the biological membrane with a high pressure jet of fluid to form a micropore of up to about 1000 xcexcm in diameter and (e) puncturing the biological membrane with short pulses of electricity to form a micropore of up to about 1000 xcexcm in diameter.
One preferred embodiment of thermally ablating the biological membrane comprises treating at least the selected area with an effective amount of a dye that exhibits strong absorption over the emission range of a pulsed light source and focusing the output of a series of pulses from the pulsed light source onto the dye such that the dye is heated sufficiently to conductively transfer beat to the stratum corneum to elevate the temperature of tissue-bound water and other vaporizable substances in the selected area above the vaporization point of the water and other vaporizable substances. Preferably, the pulsed light source emits at a wavelength that is not significantly absorbed by skin. For example, the pulsed light source can be a laser diode emitting in the range of about 630 to 1550 nm, a laser diode pumped optical parametric oscillator emitting in the range of about 700 and 3000 nm, or a member selected from the group consisting of arc lamps, incandescent lamps, and light emitting diodes. A sensing system for determining when the barrier properties of the stratum corneum have been surmounted can also be provided. One preferred sensing system comprises light collection means for receiving light reflected from the selected area and focusing the reflected light on a photodiode, a photodiode for receiving the focused light and sending a signal to a controller wherein the signal indicates a quality of the reflected light, and a controller coupled to the photodiode and to the pulsed light source for receiving the signal and for shutting off the pulsed light source when a preselected signal is received.
In another preferred embodiment, the method further comprises cooling the selected area of biological membrane and adjacent tissues with cooling means such that said selected area and adjacent tissues are in a selected cooled, steady state, condition prior to, during, and/or after poration.
In still another preferred embodiment, the method comprises ablating the biological membrane such that interstitial fluid exudes from the micropores, collecting the interstitial fluid, and analyzing the analyte in the collected interstitial fluid. After the interstitial fluid is collected, the micropore can be sealed by applying an effective amount of energy from the laser diode or other light source such that interstitial fluid remaining in the micropore is caused to coagulate. Preferably, vacuum is applied to the porated selected area to enhance collection of interstitial fluid.
In yet another preferred embodiment, the method comprises, prior to porating the biological membrane, illuminating at least the selected area with light such that the selected area illuminated with the light is sterilized.
Another preferred method of porating the biological membrane comprises contacting the selected area with a solid element such that the temperature of the selected area is raised from ambient temperature to greater than 100xc2x0 C. within about 10 nanoseconds to 50 ms and then retuing the temperature of the selected area to approximately ambient skin temperature within about 1 to 50 ms, wherein this cycle of raising the temperature and returning to approximately ambient temperature is repeated a number of time effective for reducing the barrier properties of the biological membrane. Preferably, the step of returning to approximately ambient temperature is carried out by withdrawing the solid element from contact with the biological membrane. It is also preferred to provide means for monitoring electrical impedance between the solid element and the body through the selected area of biological membrane and adjacent tissues and means for advancing the position of the solid element such that as the ablation occurs with a concomitant reduction in resistance, the advancing means advances the solid element such that the solid element is in contact with the biological membrane during heating of the solid element. Further, it is also preferred to provide means for withdrawing the solid element from contact with the biological membrane, wherein the monitoring means is capable of detecting a change in impedance associated with contacting a layer underlying the biological membrane or a layer thereof and sending a signal to the withdrawing means to withdrawn the solid element from contact with the biological membrane. The solid element can be heated by an ohmic heating element, can have a current loop having a high resistance point wherein the temperature of the high resistance point is modulated by passing a modulated electrical current through said current loop to effect the heating, or can be positioned in a modulatable alternating magnetic field of an excitation coil such that energizing the excitation coil with alternating current produces eddy currents sufficient to heat the solid element by internal ohmic losses.
A method for enhancing the transmembrane flux rate of an active pereant into a selected area of a body comprising the steps of enhancing the permeability of the biological membrane layer of the selected area of the body surface to the active permeant by means of
(a) porating the biological membrane of the selected area by means that form a micropore in the biological membrane optionally without causing serious damage to the underlying tissues and thereby reducing the barrier properties of the biological membrane to the flux of the active permeant; and
(b) contacting the porated selected area with a composition comprising an effective amount of the permeant such that the flux of the permeant into the body is enhanced.
In a preferred embodiment, the method further comprises applying energy to the porated selected area for a time and at an intensity and a frequency effective to create a fluid streaming effect and thereby enhance the transmembrane flux rate of the permeant into the body.
A method is also provided for applying a tattoo to a selected area of skin on an individual""s body surface comprising the steps of:
(a) porating the stratum corneum of the selected area by means that form a micropore in the stratum corneum optionally without causing serious damage to the underlying tissues and thereby reduce the barrier properties of the stratum corneum to the flux of a perneant; and
(b) contacting the porated selected area with a composition comprising an effective amount of a tattooing ink as a permeant such that the flux of said ink into the body is enhanced.
A method is still further provided for reducing a temporal delay in diffusion of an analyte from blood of an individual to said individual""s interstitial fluid in a selected area of biological membrane comprising applying means for cooling to said selected area of skin.
A method is yet further provided for reducing evaporation of interstitial fluid and the vapor pressure thereof, wherein said interstitial fluid is being collected from a micropore in a selected area of the biological membrane of an individual, comprising applying means for cooling to said selected area of biological membrane.
In accordance with still further embodiments, the present invention is directed to a method for delivering bioactive agents into the body through micropores formed at selected depths in a biological membrane, such as the skin or mucous membrane or outer layer of a plant. The method involves porating an outer layer of the biological membrane through any of the poration techniques known in the art, but to a sufficient and desired depth into or through the biological membrane, and contacting the porated site with an effective quantity of the bioactive agent of low or high molecular weight and size. This process can be enhanced by applying further permeation enhancement measures either before, during or after the bioactive agent is delivered. For example, sonic energy, iontophoresis, magnetic fields, electroporation, chemical permeation enhancer, osmotic pressure and atmospheric pressure measures may be applied to the porated site to enhance the permeability of layers beneath the outer layer of the biological membrane.